Various performance settings can be changed by an administrator in Settings > Site administration > Server > Performance.
Other site administration settings which may affect performance
- Make sure caches are used (they are on by default)
- Cache language menu and Cache all language strings in Settings > Site administration > Language > Language settings.
- Make sure Theme designer mode is Off in Settings > Site administration > Appearance > Themes > Theme settings (unless you are editing a theme of course!). This is the default.
- Large log files can cause overall performance to degrade over time. If you observe that the site has gradually got slower loading pages in the browser, reduce your Log life time setting in Settings > Site administration > Server > Cleanup
- Using secure web connections (https rather than http) carries a higher processing burden, both for the webserver and the client - particularly because cacheing cannot be used as effectively, so the number of file requests is likely to increase dramatically. For this reason using https for all Moodle pages is not recommended. You can enable https just for the login screen, simply from Moodle's config page.
- Check your filters. Having too many filters active can have serious effects on server load, especially on lower-end systems. The number of active filters has a direct effect on the perceived latency of your site; that is the time taken for each page impression.
- Check your anti-virus measures on the server. Although they are useful for preventing security holes being exploited, some "On-Demand" scanners can affect performance by scanning page content (word, ppt files etc).
- Check your forum settings' in Settings > Site administration > Plugins > Activities > Forum. To improve performance set Track unread posts to No (although the user's will loose the ability to track unread posts).
- Don't use database sessions unless you really need them. On-disc sessions tend to be much faster.